Many compositions are known in the art which are useful for coating substrates to produce abrasion resistant products. In particular, substrates containing acrylic, e.g., polymethyl methacrylate, or polycarbonate polymers can be coated with an abrasion resistant coating of a mixture of a multihydroxy fluorocarbon polymer and a polysilicic acid. A more hydrolytically stable coating composition, as well as one that could be cured in a shorter time at lower temperatures, was needed and it was discovered that a coating composition of the multihydroxy fluorocarbon polymer and either citric or malonic acid or an acid ester thereof filled the above-described need. However, such coating compositions could be improved upon in their resistance to abrasion and in their resistance to attack by the action of various solvents such as methylene chloride, acetone, methyl ethyl ketone, chloroform, acetic acid, ethyl acetate and the like.
It has now been discovered that thermally cured coatings derived from a coating composition of a multihydroxy fluoroolefin copolymer and a multicarboxylic aliphatic acid characterized in that the acid contains at least four carboxyl groups and has at least a four carbon atom chain and in which the carbon chain may be interrupted by oxygen or sulfur atoms, show greater resistance to abrasion and most show greater resistance to attack by solvents, greater resistance to damage by hot water and better adhesion than the coating compositions described hereinabove.